I. Field of the Invention
The present invention generally relates to methods for preparing sulfur hexafluoride. More specifically, the present invention is directed to methods employing the reaction of elemental sulfur with a metal fluoride as the fluorinating agent to produce sulfur tetrafluoride which is, in turn, reacted with oxygen to produce sulfur hexafluoride.
II. Description of the Background
Sulfur hexafluoride (SF.sub.6) is particularly stable and resistant to attack. Because of its chemical inertness, high dielectric constant and molecular weight, sulfur hexafluoride has often been used as a gaseous insulator in high voltage generators and other electrical equipment. Accordingly, safe and efficient methods for producing sulfur hexafluoride are desirable.
Sulfur hexafluoride is typically manufactured by the direct fluorination of sulfur vapor with pure, gaseous fluorine. Sulfur hexafluoride is the principal reaction product along with traces of sulfur tetrafluoride (SF.sub.4) and disulfur decafluoride (S.sub.2 F.sub.10). The reaction product of this direct formation is initially scrubbed with caustic. Any disulfur decafluoride present is decomposed by heating to about 400.degree. C. Scrubbing again with caustic removes the resulting decomposition products.
These prior methods for producing sulfur hexafluoride using pure, gaseous fluorine require the consumption of large quantites of energy in the electrolytic production of pure, gaseous fluorine. Further, fluorine, because of its extremely high reactivity and toxicity, requires special safety procedures for handling. These methods also produce polluting and, in fact, toxic waste products. Accordingly, there has been a long felt by unfulfilled need for safer, less polluting, more efficient and more economical methods for producing sulfur hexafluoride.
The present invention solves those needs.